Phone number or other contact info. Supposing you’re on good terms, they’re not someone you’re interested in romantically or the like (so none of the anxiety from that at least), what’s kept you from asking?
Supposing that something has on occasion, anyway.
I’m like this too. I also don’t ask people to hang out because I don’t want to bother them and I don’t want to just assume they like me and want to do anything together. Yeah I don’t make friends that way and it can be lonely.